Digital evidence mounting in Boston after marathon bombing

BOSTON — The Boston Marathon’s crowded finish line meant greater tragedy Monday, but it also proved key to identifying the suspects in the bombing.

Thanks to the ubiquity of security cameras and smartphones, authorities were able to release photos Thursday implicating two suspects in the Monday marathon blasts. The suspects became part of a massive man hunt, followed by a dramatic overnight shooting that left one dead and one on the run early Friday morning.

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Boston Marathon suspects photos

Hundreds of shutters snapped and cameras rolled before and after the two explosions ripped through the city’s downtown, unintentionally capturing the moment and maybe even the culprits. Faced with this deluge of images, law enforcement officials combined facial recognition technologies, digital enhancements and old-fashioned detective work to sift for clues.

“There’s no doubt no small number of FBI analysts are going through and creating folders for files of potentially relevant information,” said David Holley, a veteran investigator and the Boston office head of Kroll, a prominent risk advisory firm. “It’s going to be a painstaking process.”

Only now the procedures involve more than squinty eyes and a magnifying glass.

Agents must first determine the incident’s time frame and examine faces of everyone in that area. They’re aided by facial recognition software, which sorts through everything from most wanted lists to driver’s license databases, and link names with faces. If no match occurs, a person’s pose and the shot’s light are altered and run through the system again.

“You rotate the image to kind of create a mug shot,” said Jim Albers, vice president for government operations at MorphoTrust, a company that supplies the FBI with much of its facial recognition technology.

“Technology itself has improved significantly so that the false acceptance is less than 0.1 percent in an ideal situation,” he said. “Facial recognition is as good as a fingerprint.”

Investigators used a similar method in 2010 to capture assassins of a prominent Hamas leader in Dubai and make progress in the probe of a Times Square bombing attempt. It also aided efforts to investigate the 2005 London bombings.